The History of Measurement
Measurement
• One of the steps of the scientific methods
involves making observations.
• An observation is information gathered by
our five senses.
Types of Observations
• There are two types of observations:
• Qualitative Observations
• Quantitative Observations
Qualitative Observations
involve describing the
properties of an object
using words.
Examples of Qualitative
Observations
•
•
•
•
The fire engine is red.
The fire engine is big.
The fire engine is shiny.
The fire engine has silver doors on the
side.
Your Qualitative Observations
• Make and record five
Qualitative
Observations about
yourself.
Quantitative Observations
• Quantitative
Observations involve
measurements.
• A measurement
includes a number and
a unit.
• The following physical properties can be
measured:
– Length
– Width
– Height
– Mass
– Temperature
– Viscosity
– Density
– Etc.
History of Measurement
• Objects were measured to aid commerce.
• Many early measurements were based on
body parts.
The Cubit
• A cubit is the
distance from your
elbow to the tip of
your middle finger.
Span
• A span is the
distance between
the thumb and the
little finger while
the hand is
outstretched.
Palm
• A palm is the width
of the closed hand.
Digit
• A digit is the
distance across the
index finger.
Body Part Measurement Practice
• Measure the following using the unit
indicated:
1. Length of the room in:
1. Cubits
2. Spans
2. Length of the textbook in:
1.
2.
3.
4.
Digits
Palms
Spans
Cubits
Problems with Body Part
Measurments
1. Body part measurements are not
accurate when dealing with fractions of
body parts.
2. People have different sized body parts.
3. The ratio of cubit to span may be
different for different people.
Standard Systems of Measurement
• Standard Systems are based on some
standard to measure against.
• Early standard systems often used body
parts of the king or ruler as the standard
distance.
• When the king died, a new measurement
system would be created.
Imperial System of Measurement
• 1 foot = average length of a man’s foot
• 1 yard = average length of a legionaire’s
stride
• 1 inch = width of a thumb
Imperial System Conversions
• 12 inches = 1 foot
• 3 feet = 1 yard
• 1760 yards = 1 mile
• 1 league = 3 miles
• 6 feet = 1 fathom
• 22 yards = 1 chain
How many inches in 2.5 leagues?
• 2.5 x 3 x 1760 x 3 x 12 =
The Metric System
• In 1799, Napoleon commissioned a survey
to find the length from the equator to the
North Pole.
• One ten-millionth of this distance was
defined as a metre.
• Conversions from one unit to another
were all done by factors of 10.
SI Units of Measurement: Base
Units
Name
Symbol
Unit of
metre
m
length
kilogram
kg
mass
second
s
time
ampere
A
electric current
kelvin
K
thermodynamic
temperature
mole
mol
amount of
substance
candela
cd
luminous intensity
Your Quantitative Observations
• Make and record 5 metric quantitative
observations about yourself.
Scalars and Vectors
• Scalar Quantities include a numeral and a
unit only.
• Examples are: 75 kg, 25 seconds
• Vector Quantities includes a numeral, a
unit and a direction.
• Examples are 125 km [N], 2.4 m/s [NW],
• 9.8 m/s/s [down]
Vectors
Scalars
Displacement
Distance
Velocity
Speed
Acceleration
Acceleration
Time
Mass
Energy
Force
Electric Field
Voltage
• Position is a
vector quantity
that measures
the distance an
object is from a
reference point
and the direction
that the object is
from the
reference point.
• Displacement is
the vector
quantity that
records the
change in
position of an
object.